[CGP] Fix Complex addressing mode for offset

If the offset is differ in two addressing mode we can continue only if
ScaleReg is not set due to we will use it as merge of different offsets.

It should fix PR35799 and PR35805.

Reviewers: john.brawn, reames
Reviewed By: reames
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D41227

llvm-svn: 322056